#include<bits/stdc++.h>
#define int long long
#define endl "\n"

using namespace std;

signed main() {
	int ret = 0;
	int l, r;
	cin >> l >> r;
	for(int i = l; i <= r; i ++ ) {
		if(i % 2 == 0) {
			ret ++ ;
		}
	}
	cout << ret << endl;
	return 0;
}

